The present invention relates generally to audio generation and coding, and more particularly relates to a method and apparatus for generating and coding digital audio data using a multi-state dynamical system, such as cellular automata.
The need often arises to transmit digital audio data across communication networks (e.g., the Internet; the Plain Old Telephone System, POTS; Wireless Cellular Networks; Local Area Networks, LAN; Wide Area Networks, WAN; Satellite Communications Systems). Many applications also require digital audio data to be stored on electronic devices such as magnetic media, optical disks and flash memories. The volume of data required to encode raw audio data is large. Consider a stereo audio data sampled at 44100 samples per second and with a maximum of 16 bits used to encode each sample per channel. A one-hour recording of a raw digital music with that fidelity will occupy about 606 megabytes of storage space. To transmit such an audio file over a 56 kilobits per second communications channel (e.g., the rate supported by most POTS through modems), will take over 24.6 hours.
The best approach for dealing with the bandwidth limitation and also reduce huge storage requirement is to compress the audio data. A popular technique for compressing audio data combines transform approaches (e.g. the Discrete Cosine Transform, DCT) with a psycho-acoustic techniques. The current industry standard is the so-called MP3 format (or MPEG audio developed by the International Standards Organization International Electrochemical Committee, ISO/IEC) which uses the aforementioned approach. Various enhancements to the standard have been proposed. For example, Bolton and Fiocca, in U.S. Pat. No.5,761,636, teach a method for improving the audio compression system by a bit allocation scheme that favors certain frequency subbands. Davis, in U.S. Pat. No. 5,699,484, teach a split-band perceptual coding system that makes use predictive coding in frequency bands.
Other audio compression inventions that are based on variations of the traditional DCT transform and/or some bit allocation schemes (utilizing perceptual models) include those taught by Mitsuno et al (U.S. Pat. No. 5,590,108), Shimoyoshi et al (U.S. Pat. No. 5,548,574), Johnston (U.S. Pat. No. 5,481,614), Fielder and Davidson (U.S. Pat. No. 5,109,417), Dobson (U.S. Pat. No. 5,819,215), Davidson et al (U.S. Pat. No. 5,632,003), Anderson et al (U.S. Pat. No. 5,388,181), Sudharsanan et al (U.S. Pat. No. 5,764,698) and Herre (U.S. Pat. No. 5,781,888).
Some recent inventions (e.g., Kurt et al in U.S. Pat. No. 5,819,215) teach the use of the wavelet transform as the tool for audio compression. The bit allocation schemes on the wavelet-based compression methods are generally based on the so-called embedded zero-tree concept taught by Shapiro (U.S. Pat. Nos. 5,321,776 and 5,412,741).
In order to achieve a better compression of digital audio data, the present invention makes use of a mapping method that uses dynamical systems. The evolving fields of cellular automata are used to generate xe2x80x9csynthetic audio data.xe2x80x9d The rules governing the evolution of the dynamical system can be adjusted to produce synthetic audio data that satisfy the requirements of energy concentration in a few frequencies. One dynamical system is known as cellular automata transform (CAT), and is utilized in U.S. Pat. No. 5,677,956 by Lafe, as an apparatus for encrypting and decrypting data.
The present invention uses complex dynamical systems (e.g., cellular automata) to directly generate and code audio data. Special requirements are placed on generated data by favoring rule sets that result in predetermined audio characteristics.
According to the present invention there is provided a system for digital audio generation including the steps of determining a dynamical rule set; receiving input audio data; establishing a multi-state dynamical system using the input audio data as the initial configuration thereof; and evolving the input audio data in the dynamical system in accordance with the dynamical rule set for T time steps, to generate synthetic audio data.
According to another aspect of the present invention there is provided a method for coding digital audio data, including the steps of: receiving synthetic audio data; sampling an audio input to generate sampled audio data; and performing a forward transform to determine intensity weights associated with the synthetic audio data to reproduce the sampled audio data.
According to still another aspect of the present invention, there is provided a system for generating audio data comprising: means for determining a dynamical rule set; means for receiving input audio data; means for establishing a multi-state dynamical system using the input audio data as the initial configuration thereof; and means for evolving the input audio data in the dynamical system in accordance with the dynamical rule set for T time steps, to generate synthetic audio data.
According to yet another aspect of the present invention, there is provided a system for coding digital audio data, comprising: means for receiving synthetic audio data; means for sampling an audio input to generate sampled audio data; and means for performing a forward transform to determine intensity weights associated with the synthetic audio data to reproduce the sampled audio data.
An advantage of the present invention is the provision of a method and apparatus for audio data generation and coding which uses a dynamical system, such as cellular automata to generate audio data.
Another advantage of the present invention is the provision of a method and apparatus for audio data generation and coding, wherein the rule set governing evolution of the cellular automata can be selected to achieve audio data of specific frequency distribution.
Another advantage of the present invention is the provision of a method and apparatus for audio data generation and coding, wherein changes to the rule set governing evolution of the cellular automata results in the production of audio data of varying characteristics (e.g., frequency, timbre, duration, etc.).
Another advantage of the present invention is the provision of a method and apparatus for audio data generation and coding, wherein the rule set governing evolution of the cellular automata can be optimized so that audio data of a specified characteristic is reproduced.
Still another advantage of the present invention is the provision of a method and apparatus for audio data generation and coding which provides an efficient method for storing and/or transmitting audio data.
Still another advantage of the present invention is the provision of a method and apparatus for audio data generation and coding wherein evolving fields of a dynamical system correspond to data of desirable audio characteristics.
Still another advantage of the present invention is the provision of a method and apparatus for audio data generation and coding wherein the evolving fields of a dynamical system are utilized as the building blocks for coding digital audio.
Yet another advantage of the present invention is the provision of a method and apparatus for audio data generation and coding which provides an engine for producing synthetic sounds.
Still other advantages of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description, accompanying drawings and appended claims.